Millimeter wave surface mount filter

Abstract

A millimeter wave filter for surface mount applications includes at least one low temperature, co-fired ceramic layer defining an outer filter surface. A plurality of parallel, coupled line millimeter wavelength hairpin resonators, each formed from a single stripline or microstrip, are positioned on the outer filter surface. Each hairpin resonator is folded back upon itself into substantially parallel resonator lines.

Description

FIELD OF THE INVENTION [0001] This invention relates to the field of millimeter wave filters, and more particularly, this invention relates to millimeter wave filters, such as parallel coupled line filters formed as hairpin filters. BACKGROUND OF THE INVENTION [0002] Almost every high frequency, RF module manufactured today requires a number of filters, including millimeter wave filters. For example, a transceiver will typically have an image reject filter and one local oscillator (LO) reject filter. The estimated number of RF modules built worldwide, including cell phones, is now over 600 million. [0003] Traditionally, high performance filters at frequencies greater than 800 MHz for use in millimeter wavelength applications are designed and fabricated using dielectric resonators. Tight design and manufacturing tolerances are required to achieve a desired filter response at these high frequencies. The filter length and width usually varies as a function of frequency band, substrate ...

AI Technical Summary

Benefits of technology

[0009] It is therefore an object of the present invention to provide a millimeter wave, thick film surface mount filter as a hairpin filter with reduced size.

[0010] The present invention is a very small, low cost, high performance RF filter using standard thick film technology and manufacturing tolerances. It incorporates a unique, hairpin resonator folded upon itself and manufactured on ceramic material. No other packaging is required. It achieves high radio frequency performance using standard thick film technology while forming a high Q filter in a very small space using folded hairpin resonators. The filter can be designed for a standard surface mount assembly and can achieve high performance filtering that is desensitized to traditional critical tolerance associated with dielectric resonator technology. Thus, in accordance with the present invention, high precision filters can be achieved at a fraction of the cost of dielectric resonator filters and superior performance achieved that is greater than performances achieved with typical SAW filters, including lower insertion losses and lower group delay.

Problems solved by technology

These filters are expensive, typically $10 each at the present time, and are usually hand-tuned during fabrication.

Conventionally designed parallel, coupled line filters are not practical at and below L-band frequencies because of their large size.

Printed hairpin filters can sometimes be excessively large at L-band frequencies and are often replaced with lumped component filters.

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